1. Field of the Invention
The invention relates to a method for repairing defects in a liquid crystal display and more particularly to a method for repairing bright dot defects in display area of Liquid Crystal Display.
2. Description of the Related Art
Liquid crystal displays have become widely used, with a working principle based on alignment condition of liquid crystal molecules changing by application of an electrical field to change the path of light passing therethrough. One LCD type is passive matrix and the other active matrix. Color of each pixel is determined by current of an end transistor in the row and the start transistor in the column. Advantages of passive matrix LCD are low cost and small size, however, slow scanning speed and small viewing angle are drawbacks. In active matrix LCD, each pixel is controlled by a transistor, and scanning is fast.
The active matrix LCD includes more than million transistors and display units, each display unit consisting of three sub display units (R, G and B).
Dot defects are formed during process of the active matrix LCD, creating light or dark defects. LCD units having fewer than five dot defects are judged as A class, however, because light defects, light defects are more noticeable to users, they are repaired into dark defects.
There are many causes of light defects, such as particles between the array substrate and the color filter substrate. Referring to FIG. 1, 110 is a signal line, 120 is a gate line, 130 is a pixel electrode, 140 is a particle and 160 is a TFT. When a particle 140 occurs in the pixel electrode region 130, the pixel cannot maintain sufficient charge. In FIG. 2, 140 is a particle, 132 is a color filter, 134 is an ITO electrode, 155 is a substrate and 130 is a pixel electrode. Because the particle 140 occurs in the pixel, signals transfer from TFT 160 (array substrate side) to the ITO electrode 134 (color filter side), causing a bright dot.
In general, bright dot defects caused by particles in the pixel are repaired by directly or indirectly shorting TFT or other repair circuit by laser to link pixel electrode and gate line or signal line, however, these methods cannot repair light defects formed by particles in the pixel since voltage of signal line or scan line will be lost from array substrate side to the color filter side, causing vertical-line type defects, horizontal-line type defects or cross-line type defects.